Great Crank Debate

[cobrajam]

I have the following cranks at my disposal to go in an Alum 427 Shelby block. I will be using a Dove tunnelwedge 4V intake, Stage III Edelbrock ported heads, 12.5:1 compression Wiseco pistons, most likely a Comp Roller Cam .730/.750 lift, aluminum flywheel, lightweight clutch assembly, Romac steel/alum lightweight balancer and plan to spin to 7500rpm. All are .010/.010 and 3.78 stroke. If the pic posts properly, they are from left to right:
64lb cast 390 truck 2U crank that has been lightened a couple of pounds by smoothing all the casting lines, removing the irregularities, and polishing the throws. Could ultimately remove another 5-10lbs.
74lb forged steel C5AE-C crossdrilled crank w/ the press-in type plugs.
65lb forged steel 391FT D2TE-EA crank, that has the snout and flywheel flange machined to work in a FE, at least 10lbs was removed by lightening and knife edging the throws.
Not pictured, a 64lb cast 427 crank with the grooved mains.

I am trying to build an FE that runs almost like an electric motor, as in a light rotating assembly. Would like an opinion on which crank you think would work best and why. In addition, looking for strong lightweight connecting rods that weigh in the 750gram range. I have some aftermarket I-beams w/ARP 2000 bolts that weigh 800grams, is there anyway weight can be safety removed from them.

[blykins]

I would go with the FT crank. Forged cranks are great if you can find them. I know some aftermarket suppliers are making new forged cranks, but I haven't heard enough feedback from them yet. So if you wanna go forged, you're left with the 427 $ cranks or the FT cranks. Since yours has already had the snout and flywheel flange machined, you're good to go. Plus the weight is really good for a forged piece.

As for the rods, I would go with an H-beam rod. You'll need the extra strength that an I-beam won't provide at your power and rpm level.

To help your engine rev, don't forget about the lightened valvetrain pieces.

[CHANMADD]

Also if you want revs get as long a rod as possible,at least a 6" rod H beam and be sure to have everything properly balanced.Don't use anything"out the box".

[cobrajam]

Plan to keep everything pretty much stock dimensions, i.e. 3.78 stroke, 6.49 rod length, the only variant being the .030 overbore. I am kind of going against the current trend of megaboring and megastroking it. If I recall correctly, Desktop Dyno pegs it at about 431ci. A lightweight roller valvetrain is in the plans. Where can you get strong lightweight H-beam rods? Eagles typically are 800gram+. Any way to lighten them some w/o sacrificing strength? Would like to find something that is closer to the stock rod weight of 725-750gr.
At any rate, I have 2 blocks and 4 cranks, may be looking to sell off the spare cranks. And by the way, the crossdrilled crank is fresh, it just has a layer of protective slime on it, thats why it looks so white.

[blykins]

I wouldn't worry about the weight of the rods. I'd find a good lightweight custom forged piston to offset the difference.

Doesn't Eagle/Scat make some lightweight versions? I'll check my catalogs.

[82ACAUTOCRAFT]

For myself, I am going to go middle ground, (3.98") 428 stroke and (4.25") 427 bores. This should make a good motor for the street! It is still oversquare with a ratio of 1.06

[Keithc8]

The thing that you need to be worried about is the rod journal diameter. The best way to go would be a 2.200 stroke and use the Truck steel crankshaft that has been lightened. I would go with a Crower or Oliver lightweight rod. The longer rod like a 6.700 or 6.800 would also let you get a lighter piston done with a BBC pin size which would give you some good choices on a light weight wrist pin. You will also need a good rocker arm system like the T&D or you will probably have valve train problems at that rpm. Think about the complete build as a package and make all of the parts work together to achieve the power and rpm you want. Good luck, Keith Craft